WASM support

[jijjijj]

General overview:

• Added WASM.h that implements the basic functions using wasm_-intrinsics
• Added auto-detection of WASM availability during compilation via macros
• Updated CMakeLists for it to automatically detect WASM/Emscripten and exclude/include corresponding files
• Added FASTNOISE2_SCALAR_ONLY Cmake option in order for consumers to be able to build scalar-only version of library (may be useful for some other exotic platform that doesn't [fully] support SIMD)
• Updated SIMDUnitTest.cpp to support WASM

Some notes:

• All test except for InvSqrt_f32 are passing. The InvSqrt_f32 is implemented as full-precision reciprocal of square root, so I guess it's failing tests because of its full precision

  Some of the failing InvSqrt_f32 tests

  InvSqrt_f32 - Base: 1 Testing: 131072
  FastSIMDTest.js:1700 131072 Failed: expected: 31294143183454208.000000 actual: 31310464059179008.000000 index: 0 floats: 0.000000 : 1313019.625000
  FastSIMDTest.js:1700 131072 Failed: expected: 0.000000 actual: 0.000000 index: 1 floats: 8604068347904.000000 : -0.000000
  FastSIMDTest.js:1700 131072 Failed: expected: 0.000018 actual: 0.000018 index: 2 floats: 3244607232.000000 : -11488148214748940590763349130583474176.000000
  FastSIMDTest.js:1700 131072 Failed: expected: inf actual: -nan index: 3 floats: -1923216266592583265009398455124099072.000000 : -0.000000
  FastSIMDTest.js:1700 131072 Failed: expected: 0.001827 actual: 0.001827 index: 4 floats: 299713.687500 : 111849439645889771479512895193088.000000
  FastSIMDTest.js:1700 131072 Failed: expected: inf actual: -nan index: 5 floats: -11258954752.000000 : -0.000000
  FastSIMDTest.js:1700 131072 Failed: expected: -0.000000 actual: -nan index: 6 floats: -0.000000 : -0.174112
  FastSIMDTest.js:1700 131072 Failed: expected: inf actual: -nan index: 7 floats: -1.335780 : -0.000000
  FastSIMDTest.js:1700 131072 Failed: expected: inf actual: -nan index: 8 floats: -273326452056742952960.000000 : -2112412712960.000000
  FastSIMDTest.js:1700 131072 Failed: expected: 0.000875 actual: 0.000875 index: 9 floats: 1305859.000000 : -701039232.000000
  FastSIMDTest.js:1700 131072 Failed: expected: inf actual: -nan index: 10 floats: -15170661.000000 : -0.000000
  FastSIMDTest.js:1700 131072 Failed: expected: 1302237708025856.000000 actual: 1303441506828288.000000 index: 11 floats: 0.000000 : -0.367376
  FastSIMDTest.js:1700 131072 Failed: expected: inf actual: -nan index: 12 floats: -96608.437500 : 6807990731479711744.000000
  FastSIMDTest.js:1700 131072 Failed: expected: 194.009384 actual: 194.285385 index: 13 floats: 0.000026 : -0.000000
  FastSIMDTest.js:1700 131072 Failed: expected: 0.000000 actual: 0.000000 index: 14 floats: 21103273522822519426383872.000000 : 0.758328
  FastSIMDTest.js:1700 131072 Failed: expected: 49713444.000000 actual: 49768484.000000 index: 15 floats: 0.000000 : -0.000000
  FastSIMDTest.js:1700 131072 Failed: expected: -0.000000 actual: -nan index: 16 floats: -0.000000 : -0.000000
  FastSIMDTest.js:1700 131072 Failed: expected: 51243980658049024.000000 actual: 51261894966640640.000000 index: 17 floats: 0.000000 : 0.000000
  FastSIMDTest.js:1700 131072 Failed: expected: 218101.359375 actual: 218351.937500 index: 18 floats: 0.000000 : -0.000000
  FastSIMDTest.js:1700 131072 Failed: expected: 4310046389305344.000000 actual: 4311402525229056.000000 index: 19 floats: 0.000000 : -150550944.000000
  FastSIMDTest.js:1700 131072 Failed: expected: inf actual: -nan index: 20 floats: -10434533376.000000 : 13898.254883
  FastSIMDTest.js:1700 131072 Failed: expected: 0.004411 actual: 0.004413 index: 21 floats: 51358.746094 : 0.000000
  FastSIMDTest.js:1700 131072 Failed: expected: 1347171072.000000 actual: 1349515904.000000 index: 22 floats: 0.000000 : 0.000000
  FastSIMDTest.js:1700 131072 Failed: expected: 806315.000000 actual: 807561.375000 index: 23 floats: 0.000000 : -0.000003
  FastSIMDTest.js:1700 131072 Failed: expected: 0.000106 actual: 0.000106 index: 24 floats: 88301032.000000 : -0.000000
  FastSIMDTest.js:1700 131072 Failed: expected: inf actual: -nan index: 25 floats: -501616.906250 : -0.000000
  FastSIMDTest.js:1700 131072 Failed: expected: inf actual: -nan index: 26 floats: -39.919510 : -6267.018555
  FastSIMDTest.js:1700 131072 Failed: expected: -0.000000 actual: -nan index: 27 floats: -0.000000 : 6.684000
  FastSIMDTest.js:1700 131072 Failed: expected: 0.000000 actual: 0.000000 index: 28 floats: 242161749151439070387672872648704.000000 : 0.000000
  FastSIMDTest.js:1700 131072 Failed: expected: 0.000001 actual: 0.000001 index: 29 floats: 1274028883968.000000 : -0.000000
  FastSIMDTest.js:1700 131072 Failed: expected: -0.000000 actual: -nan index: 30 floats: -0.004396 : -75414865430546055430144.000000
  FastSIMDTest.js:1700 131072 Failed: expected: 1653474944.000000 actual: 1656043520.000000 index: 31 floats: 0.000000 : 0.000000
  

• I added target_link_options(FastNoise PRIVATE -sALLOW_MEMORY_GROWTH=1) in the main CMakeLists and the one for tests. Maybe that wasn't a good idea, because a consumer-application may want to control this property

• At WASM.h:132 I use __f32x4 as underlying type but it's actually an internal type and not a user-facing one. However without it some of the functions won't work as expected

• I didn't try to compile the NoiseTool, since it's outside of scope of my work, so I don't know if it works

• The only tests I ran were the ones in "SIMDUnitTest.cpp", let me know if there are other tests I need to check